1. Field of the Invention
This invention is directed to improved lubricant compositions comprising hydrocarbyl diphenyl ethers alone or in combination with synthetic or mineral oil fluids, and to mineral or synthetic lubricant compositions containing said ethers as additives therefor.
2. Description of Related Art
Polyphenyl ethers are known and have been used as lubricants in special applications. Polyphenyl ethers suffer from very high cost due to difficult synthesis and poor low temperature viscometrics.
Polyphenyl ethers are known for their high temperature properties as noted in D. Klamen's "Lubricants and Related Products", Verlag Chemie, 1984, pp. 116-121, and references contained therein, and also in, for example, the product bulletin for the commercial polyphenyl ether, OS-124 by Monsanto.
Many alkylation processes are known in the art and the alkylation methods of much of the prior art are primarily directed to polysubstituted or polyalkylated products. See, for example, JA 5557391 to Matsumura which discloses the dialkylation of diphenyl ethers over aluminum chloride. U.S. Pat. No. 4,395,372 to Klutz discloses the alkylation of benzene over a zeolite to obtain a predominantly polyalkylated product unless the alkylation takes place in the presence of sulfur dioxide. On the other hand U.S. Pat. No. 4,664,829 to Arakawa alkylates a mixture of materials to obtain both mono- and polysubstituted material. Arakawa uses Friedel-Crafts type catalysts. Garces, U.S. Pat. No. 4,891,448 discloses the alkylation of polycyclic aromatics over natural zeolites such as mordenite, offretite and gmelinite.
The present invention is directed to the alkylation of diphenyl ethers over zeolite catalysts which surprisingly results in a product which is predominantly or almost completely monoalkylated. Synthesized catalysts are preferred. Monoalkylated product comprises up to at least about 99% of the alkylation process in accordance with the present invention. In some instances the monoalkylation rate is 100%.
Incorporation of linear alkyl hydrocarbon groups into diphenyl ether eliminates the above-referenced problems and provides a novel, relatively inexpensive lubricant having excellent low temperature viscometrics. The use of these adducts as a lubricant or lubricant additive in either mineral or synthetic lubricants is unique and provides improved properties and performance benefits due to an inherent synergism.